Amplifier circuit having reactive load



July 2 5, 1950 B. M. OLIVER AMPLIFIER CIRCUIT HAVING REACTIVE LOAD 5 Sheets-Sheet 1 Filed Feb. 28, 1948 FIG. I

rm 4 L I08 wa CA77-IODE RAY rues AMPLIFIER snwroorn WA VE GENERATOR FIG 2) smcrmomzuvs PULSES FIG. 2

IOJ L: 1'0 AMP. m4

SYNCHRON/Z/NG PULSE:

INVEN TOR B BM. OLIVER AT T ORNE V July 25, 1950 B. M. OLIVER AMPLIFIER CIRCUIT HAVING REACTIVE LOAD Filed Feb. 28, 1948 5 Sheets-Sheet 2 R 365 I Ldklbu I o&

WIN/14;

ATTORNEY y- 1950 I B. M. OLIVER 2,516,797

AMPLIFIER CIRCUIT HAVING REACTIVE LOAD Filed Feb. 28, 1948 5 Sheets-Sheet 3 70x85 T0 SUPPLY 72/ mm: OF I Fm runs: 709 a m 722 750a v v K TERM/ML 7/6 756 7 752 0F call. 714 FIG. 6a NEGATIVE V VOLTAGE cum/r755 l 753 l 75/ TERMINAL 7/: FIG. 66 0F can 714 men you: 762

ourpur 77.; FIG. 6 c

v 778 T0 SUPPLY 72/ man vomlcs :l: m;w 7/5 4 INVENTOR y B. M. OLIVER ATTORNEY July 25, 1950 B. M. OLIVER 2,516,797

AMPLIFIER CIRCUIT HAVING REACTIVE LOAD Filed Feb. 28, 1948 5 Sheets-Sheet 5 PLATE VOLTAGE FOR runs 709 VOLTA 6E F7617]: T PLATE VOLTAGE I F0)? TUBE 7/0 VOLTAGE PLATE CURRENT IN TUBE 709 CURRENT PLATE CURRENT IN TUBE 7/0 msr cuR/mv'r I SUPPLIED Br 807/! runs 709 a no 7'0 LOAD CURRENT 7mm. CHARGING CURRENT CAPACITIES FIG. 71

TOTAL EFFECTIVE CURRENT SUPPL IE 0 TO OUTPUT TRANSFORMER CURRENT INVENTOR B B. M. OLIVER I lm A TTORNEY Patented July 25, 1950 Bernard Mi. 0liver,-.New York, N;. Y'., assignonjto Bell 'llelephoneLahoratories, Incorporated New- York, N. Y a corporation of New York Application February 28, 1948, SerialNb- 1 3 Glaims. I

This invention relates to amplifier circuits and more specifically to that type of amplifier cir-v cui-t=-usedto drive a reactive load; such as, for example. the sweep coils for producing defiection of the beam in a cathode ray tube;

It is an object of this invention toincrease: the efiiciency of amplifiers which are used to drive reactive loads.

If a straightforward class A amplifier is used to drive the horizontal deflection coils in a high.

voltage television cathode ray tube, a large amount of plate-power is required. This is because considerable energy is stored in the reactive load each cycle and then wasted during the'fly-back time. To-avoidthis waste, a variety of circuits, called booster circuits employing damper tubes have been used. These-circuits are widely used today in. home television receivers. They have the considerable drawback, however, of being hardto adjust. A number of controls are required and these controls are interdependent; Thus the control called horizontal size aiiects the linearity and the one called horizontal linearity aiTects the size, etc. Even with a fortuitous adjustment the results are far from satisfactory. The present invention, in one of its primary aspectsrelates to an amplifier circuit for applying sweep waves to the deflecting coils of a high voltage cathode ray television tube and in which these defects are minimized.

It is an object of this invention to decrease It is still another object of this invention to obtain a supply of high voltage from an. amplifier circuit for deflecting waves without afiecting the fiy-back time of the wave or the drain.

of power from the source used. to voltage to the amplifier.

These and other objects are attained. in accordance with an exemplary embodiment of the invention by providing-a circuit for driving the deflecting coils of a cathode ray tube (such as in. a television receiver) comprising two. tubes operated in push-pull manner under class. 3

supply. plate off thesestubes. draws: its. plate. power; (for one:- half of. thedeflecting portionof each sweep. Wave cycle) from: the. energy-"stored. in the reactive load by: the. other tubei during the other halfiof. the deflecting; portion Ofithfi sweenwave cycle. Thisireactiveload can be either. the. deflecting; coilsor'a transtormer'connected to..them. This; stored energy is also; sufficient to provide. high. voltage tor the beam. acceleration; inthe cathode ray. tube. or for other.- purposes. without. any increase in consumption from the-.B=supply. providing the plate. powers. By.- employing a...feedback connection niomthe output. of thisampli: fier. circuit tcthe input; thereof, it ispossible to, attain the high. degree or linearity heretofore obtainable. not only with. high. current drain; cite. cuits. but with a; power. consumption. comparable to or lessthan; that. of existing. present-day 0,11:-

cuits having: poor. output... linearity. 2c.

I netic deflection: systemior a. cathode ray. beam, the system embodying an. amplifier circuit? in ac.-

cordance. with. thev invention;

Fig. 2 is a. schematic diagram. of. the: saw-tooth generator usediin theisystem .of Fig.1;

Fig. 3' is. a. schematic diagram. of: the first am-. plifier used in: the system. of Fig. 1;...

Fig. 4 isra schematic diagramof the. output stageiamplifien in the systemof Fig. 1 together: with the. reactive: load therefor; Fig. dis a schematic diagram Ofia, protective circuit: which I can. bev used: as: part of the circuit Referring morez'sp ciflcally to; he drawin s;

Fig. 11 showsby: Way of example iorpurposes. of; iHHSUZdfiOflLfiHd? in lq lrzschemat f rm, a; d b flectionv system: for a ma net cally defle ca hode, ray tub "10:. The defl onv rs em c udes a woq iwa e enerates "l2 own.- in: greater? detail; in: Fig; 2)., a first. amplifier i04- conditionsand characterizedby thefact that. one 55; 'shownrinigrea erde ail iii-Fig.2 3-) ,and an enteput stage amplifier I01 the output circuit of which is connected to deflecting coils I08 for the cathode ray tube I (the amplifier I01 and its load being shown in greater detail in Fig. 4). Synchronizing pulses of any well-known form such as the horizontal or vertical synchronizing pulses produced from the standard RMA television signal, for example, are applied to the terminal IOI of the saw-tooth wave generator I02.

In response to these pulses the saw-tooth wave generator I02 produces a series of saw-tooth voltage waves which appear at terminal I03. The first amplifier I04 amplifies these waves and by means of a phase splitter or phase inverter stage produces a balanced or push-pull output on the leads I05 and I06. The waves on lead I05 are in the same sense as theinput to the amplifier while those on lead I06 are in the opposite sense. The waves on leads I05 and I00 are applied as a balanced input to the output stage amplifier I01 which drives .the deflection coils I08 with a saw-tooth 'wave form of current. Preferably a resistor I09 is in series with the defiection coils I08. The voltage across this resistor, which is a measure of the current in the coils I08, is fed back by way of lead IIO to the input amplifier I04. By means of this feedback connection, the current in thedeflection coils I08 can be made to correspond closely to the input voltage of the first amplifier I04, as is well known in the art.

While the invention relates primarily to the novel circuit arrangement of the first and output stage amplifiers I04 and I01 and to various power utilization circuits which are associated therewith, nevertheless, to aid in the understanding and the operation of the entire system, a brief description of a satisfactory saw-tooth wave generator I02 will first be given.

Referring now to Fig. 2, the sweep generator I02 comprises four tubes 203, 201, 2I4 and 2I0 and circuit elements associated therewith. Negative synchronizing pulses .having the form shown in Fig. 7a are applied to the terminal IOI and, by means of the coupling condenser 20I, to the grid of the tube 203. This tube is normally conducting current between pulses as its grid is held at substantially cathode potential by the flow of current through resistor 202. During each synchronizing pulse, this tube 203 is cut oif and the cessation of plate current causes a positive voltage pulse to appear across the resistor 204 in its plate circuit. This positive pulse is applied through the coupling condenser 205 to the grid of the tube 201.. Tube. 201 is normally non-conducting as a result of the positive voltage developed across the parallel combination of the resistor 208 and the condenser 200 in its cathode circuit by the average plate current. When the positive pulses, which are similar to those shown in Fig. 1b, are. applied tov the grid of the tube 201, this tube conducts a large amount of plate current. The resistance. of the resistors 2H], 2 I2 and 2I3 is so great that during the pulse, most of the plate current required by the tube 201 is drawn through the condenser 2 from the cathode of the tube 2I4. The condenser 2I I becomes charged somewhat asa result, but is discharged between pulses by current through the resistors 2 I0, 2I2 and 2 I3. Resistors 2I2 and 2I3 are so proportioned that when tube 201 is non-conducting (between pulses) the cathode of tube 2 I4 is morepositive than either the grid or plateof this tube. 'As a result, no plate current flows in tube 2'I4 between pulses.- During each pulse, however, the cathode potential of tube 2I4 drops, as shown in Fig. 70, until the current required by tube 201 can be supplied by space current in tube 2I4. Part of this space current is drawn as grid current in the tube and part as plate current. The plate current discharges sweep condenser 2I5 until the plate of tube 2I4 drops to cathode potential. The remainder of the cathode current drawn by tube 2I4 is then drawn from the grid. As a result, at the end of the synchronizing pulse, all of the elements of tube 2I4, as well as the upper terminal of condenser 2I5, are substantially at the positive potential of the supply 222. This supply is shown for convenience as a separate voltage source, but can, in practice, be a voltage divider across supply 22I. After each pulse, the positive potential of the cathode of tube 2I4 increases again and no further plate current flows in this tube until the next pulse.

Condenser 2I5 now starts to recharge as a result of current supplied by the source 22! through resistors 2 I6 and 2I1. As is well known, this recharge would normally be along an exponential curve. However, the upper (ungrounded) terminal of condenser 2I5 is also connected to the grid of tube 2I8. In the cathode circuit of this tube is a high resistance 2I9. As the grid voltage of tube 2I8 changes, comparatively little change in the grid to cathode voltage of tube 2I8 is required to supply the change in current required by resistor 2I9 and the associated circuit. As a result, the cathode potential of tube 2I8 closely follows changes in the grid potential of this tube. The voltage wave across condenser 2I5 is therefore accurately reproduced at the output terminal I03. This wave is also applied through coupling condenser 220 to the junction between resistors 2| 0 and 2I1. Since any change in potential of the lower end of resistor 2I6 as shown in Fig. 2 produces an equal change in potential of the upper end of this resistor, the voltage across resistor 2I6 is constant, and a constant current flows in this resistor. Fig. 7d shows the voltage waves on the two ends of resistor 2I6. The constant current through resistor 2I6 recharges condenser 2I5 at a constant rate and a linear rise of voltage with time is produced and appears at the output terminal I03.

Referring now to Fig. 3, which is a schematic diagram of the amplifier I04, the output of the saw-tooth wave generator is applied to terminal I03. The amplifier I04 comprises a first amplifying stage comprising tube 403, a phase splitter" stage comprising tube 409, and a balanced third stage comprising tubes 4" and M8 which stage acts as a driver for the output stage amplifier I01 of Fig. 4. Voltage variations of terminal I03 are applied to the grid of tube 403 through coupling condenser 40L If negative feedback from the deflection coils is used, the voltage across resistor I09 (of Figs. 1 and 4) can be applied through feedback lead IEO (shown dotted) and condenser 422 to the cathode of tube 403. The plate current in tube 403 then varies in accordance with the variations in the difierence of potential between leads I03 and III]. The amplified voltage developed aoross resistor 405 is applied through condenser 406 to the grid of tube 409. The grid of tube 409 is held at a positive potential by resistors 401 and 408 acting as a voltage divider across the supply 42I. The cathode of this tube is connected to. ground through resistor M0 and the plate is connected to the positive ter- 5:" glinedtli of the supply-42I through an equal resisor I. through equal resistors 41B and 4 produces a positive voltage on the cathode, of this tube and an equal voltage drop across resistor 4| I. Any plate current change produces equal and opposite voltage changes on the plate and cathode. The cathode voltage varies in the same sense as the-grid voltage while the plate voltage varies in the opposite sense. The-tube 409 thus acts as a phase splitter and its balanced output voltages areapplied through condensers 412 and M3 to the grids of tubes 4|! and M8, respectively; These two tubes are connected as a push-pull class A amplifier stage in the manner shown, which is well known in the art, resistors 4M and M5 being the grid resistors, 4H5 the cathode bias resistor, and sis and 428 the plate load resistors. The balanced or push-pull output waves appear across terminals i135 and I08.

Fig. 4 shows a circuit arrangement of the output stage amplifier Hi7 and its reactive load. The amplifier H11 comprises tubes 109 and N the input circuits of which are connected in the usual push-pull fashion and the output circuits of which are connected in novel manner to the primary windings l l 3 and I l 4 of an output transformer H9. The balanced output voltage waves, of the amplifier H34, appearing on leads I05 and H36 are applied through coupling condensers HH and H52 to the control grids of tubes I09 and 1 l0, respectively. The sense of the saw-tooth waves is such that during the linear or forward portion of the sweep cycle the potential of the control grid of tube hi9 becomes less and less negative while the control grid of tube ll!) becomes more and more negative. Then during the sudden return or fly-back portion of the cycle the control grid of tube R39 again drops more negative in potential while the control grid of tube 1 l 0 rises to a less negative potential. The two grid waves are illustrated in Figs. 7c and U, for tubes H19v and lit, respectively. The average control grid potential of tube N39 is held negative by resistors 161 and me, together with part of potentiometer 19G acting as a voltage divider across negative supply m5, while the rid of tube H8 is held negative by the similar arrangement comprising resistors its and T04 and the rest of potentiometer E66. Potentiometer m6 serves to adjust the relative control grid potentials and thus to balance the operation of the tubes as will be explainedlater. The screen grids of tubes and Hit are held at a positive potential during the forwardportion of the cycle by the screen supply IZU, the function of which will also beexplained later in connection with Fig. 5. The cathodes of both tubes H19 and Hi] are connected to ground. The plate of tube I09 is connected to the positive supply l2! of voltage EB through the primary winding N3 of output transformer H9, while the plate of tube '5 I9 is connected through the other primary winding N4 of the output transformer l l 9 to ground, or to a power utilization device E50 indicated by the dotted rectangle. Typical power" utilization devices will be described later in connection with Fig. 6. The secondary-winding ll] of the output transformer I I9 is connected to the deflection coils I08 of the cathode ray tube E60. As mentioned before, a resistor H19 can be included in this output circuit to develop a feedback voltage on lead H0. The two primary windings H3 and N4 of the output transformer arewound series aiding as in a conventional push-pull output transformer The plate current of tube 409 flowing and in. a preferred arrangement have substan tially the same number of turns. The output transformer H9 preferably also includes an ,elec-' trostatic shield l l 3 between the primary windings 1 l3 and H4 and the secondary winding H1. The

distributed or stray capacity associated with the transformer and the plates of tubes [09 and H0 are indicatedby the-two capacities Hi and "H2 designated 0/2 in the drawing.

The cycle of operation of the circuit of Fig.4 will now be described. The control grids of the tubes H39 and H0 are so biased that at a time t1 corresponding tothe middle of the forward portion of the input waves, both tubes are substantially cut off (i.e., non-conducting) as indicated in Figs. 7e and 7f. As'time proceeds, tube H0 is completely cut off while the control grid potential of tube 109 becomes less negative. Accordingly, plate current in tube 109 increases in a substantially linear fashion as shown in Fig. W. The linear increase in plate current in tube 109 causes the plate voltage of this tube to be lowered to a value EBEL, where Es=voltage of supply 721 ch n v L=inductiance of winding 713 with deflecting coils 108 connected to winding 717 I t=time.

If windings H3 and H4 are equal, a positive voltage EL is present on the plate of tube 'Illlduring the forward portion of the cycle. The plate volt.-

age waves for tubes 199 and ill! are shown in.

Figs. lg and 7h, respectively.

At the time 262, the plate current in tube 109 reaches the value I. At this time the grid voltage of tube 169 is driven negative by the input wave (Fig. 7e) and the plate current drops to zero. This sudden stoppage of plate current in tube 109 induces a transient in the load circuit causing the platevoltage of .tube Hi9 to be driven very positive and the plate voltage of tube 7 i 0 to be driven very negative. During this time,

indicated as T in the figures, neither tube 509 nor tube lit can, therefore, conduct plate current. Tube ":09 cannot conduct because of the highly negative grid voltage, while tube 1 I it cannot conduct plate current because the plate voltage is negative. A current step of magnitude I is thus introduced to the load (at time tain Fig. 72'). The load transient, assuming the damping to be small, is a, substantiallysinusoidal oscillation of" angular frequency same sense as the first step from tube m9 at time f2. The load transient from this second step,

beingone half cycle later, is directly outof phase with the transient from the first step and the two waves cancel, leaving the plate of tube H0 at the potential vEL, and a current I in winding H4.-

.Thecontrol grid potential. of tube 1 I I! .now. I goes more negative decreasing the plate current in a linear fashion until the middle of the cycle is again reached at time t4=t1+T, where T=duration of one complete saw-tooth cycle. At the time t4, tube I09 again takes over, and the cycle repeats.

Actually, because of small losses in the load circuit, the oscillation will decay slightly during the fly-back time and the peak current demanded from tube H will be slightly less than the peak current in tube 109. To correct for this effect, and for possible mismatch between tubes 109 and H0, the potentiometer 106 is included. By adjusting this potentiometer the onset of current in tube H0 can be controlled so as to cancel completely the fly-back transient. If feedback is used around the amplifier, the setting of potentiometer I06 is not critical.

The plate current cycle of tube 109 is shown in Fig. 71', while that of tube H0 is shown in Fig. '7 The difference between these two currents, which is the net current supplied by both tubes to the load, is shown in Fig. 774:. Fig. 71 shows the total charging current into the two stray capacities H I and H2. The Sum of the currents in Figs. 7k and ll is the total effective current (Fig. 7m) supplied to the output transformer. It will be seen that the current in Fig. 7m consists of a series of saw-tooth waves having a linearly increasing (forward) portion, and a sinusoidally decreasing (fly-back) portion. The peak to peak value of this wave is 2I.

In practice, the return or fly-back time of the waves, 1-, would be a much smaller fraction of the total cycle time, T, than the proportions shown in the figures.

The average plate current in tube 709 is seen from Fig. '71 to be roughly This is the only plate current drain on the supply 12 l. Neglecting screen currents, then (since these are relatively small) the total current drain from the power supply 121 is roughly A; of the peak to peak sweep current referred to the primary of the output transformer. If a single tube were used as a class A amplifier in the output stage instead of the push-pull arrangement described above, the peak plate current required in this tube, for the same output power as before, would be at least 2I. The average current would be at least I, and all of this current would be drawn from the plate power supply. Accordingly, the plate power requirement of the output stage according to this invention is roughly that for a conventional unbalanced (i. e., not push-pull) class A output stage.

The plate power requirement of a conventional sweep amplifier output stage is sometimes reduced by the use of a so-called damper tube or damping diode shunted across the deflecting coils. This tube is poled so as to conduct during the first half of the forward portion of the sweep wave, at the end of the fly-back time. This damping tube thus supplies a pulse of current to the load somewhat analogous to the current supplied by tube H0 in the present circuit. Accordingly, the sweep amplifier tube proper can be nearly cut off for this time and the plate power drain is reduced. If the current pulse in the damper tube can be made a proper supplement to the current in the amplifier tube a linear sweep wave can be obtained. However, this is diflicult to doin practice, and good results are rarely-obtained. Negative feedback cannot be effectively used with this type of circuit to linearize the sweep because during part of the forward portion of the sweep wave, the amplifier tube is non-conducting and no loop transmission exists.

In the present circuit, the plate current waves of tubes 709 and H0 are naturally supplementary as in a conventional, linear, push-pull class B amplifier, and relative unbalances between the tubes can be largely compensated through proper adjustment of the relative grid biases using potentiometer 108. In addition, negative feedback can be used with the present circuit to attain a very high degree of sweep linearity, since transmission is always present either through tube 109 or HD or both.

During the interval T, the control grid of tube H0 is at a potential such that the tube would conduct a large plate current if the plate were positive. Consequently a large screen grid current may be drawn by tube 1 l 0 during this time if the screens were connected directly to the positive terminal of supply 12!. If the interval 1- is an appreciably large fraction of the total cycle, the normal screen dissipation in this tube may be exceeded and the current drain from supply 'lZI materially increased. To prevent this, the screen current for tube lit (and, as shown, for tube 109 also) can be drawn from a special supply device l29. A schematic diagram of a suitable device ior this purpose is shown in Fig. 5. The screen grids of tubes 109 and H0 are connected to terminal 723. This terminal is connected to the plate of diode 121 and also through resistor "24 and inductance 125 to a positive voltage supply, 126, of voltage E0. The cathode of diode 721 is connected to the positive supply 121 (in Fig. 4) of voltage EB. E0 is assumed to be more positive than EB. Resistor 724 is so chosen that the current through it, I0, is slightly greater than the maximum screen current drawn by either tube #09 and HE! during the forward portion of the cycle. Diode T21 accordingly conducts the excess current during this time and fixes the potential of terminal 123 to be only slightly more positive than terminal 422. When tube H0, during fly-back, attempts to draw screen current in excess of Io, the diode 12'! stops conducting and the potential of terminal 523 falls. Inductance T25 prevents the current to the screen from rising materially above the value In during the time 1-. In practice, supply 72! can be an electronically regulated power supply, and supply 126 can then be merely a tap on the unregulated voltage developed within this supply.

If the interval 1- is suificiently short, as will often be the case in practice, screen supply ,can be omitted and the screens of tubes 109 and fiawthis curve to represent the characteristic with and is indicated as EB-EL in the figure. The

energy stored in the load is proportional to the shaded area in the figure, i; e., energy in load. at

Ina proper design, L is chosen- (by a suitable turns ratio in the output transformer) so that the shaded area in 8 (ELI) is maximized. When this is done, the proportions are approximately as shown in Fig. 8. If the windings H3 and N4 of the output transformer are equal, tube Hi1 will now have. a positive plate voltage of E1. during the forward part of the cycle- .Actually a plate voltage of EB-EL is suflicient to allow tube H to conduct the maximum required current I. In other words, with the inner end HE of winding connected toground as shown in Fig. 4, the plate voltage on tube H0 during the forward portion of the cycle is higher than necessary by an amount 2EL-EB. H5 can be connected to any one of several types of power utilization devices and an amount of power equal to ion-EB) can be delivered to this device. This excess power would otherwise be dissipated at the plate of tube Hil. Typical power utilization devices are shown in Figs. 6a, 6b and 60.

Referring to Fig. 6a, the terminal N5 of the transformer winding lid is shown connected to a large condenser #54, the lower end of which is grounded. The plate current pulses passed by tube H0 are drawn from this condenser. As this action proceeds, the top plate of condenser l5lbecomes negatively charged. This top plate of condenser i5! is connected through a small resistor 752 to the cathode of a gas tube 753. The anode of this gas tube is grounded. When the voltage across the condenser l5! reaches a predetermined value, equal to or less than 2Er.-EB, the gas tube 153 breaks down, and by conducting the excess current, prevents any appreciable further increase in voltage across condenser 15L Also connected to the cathode of the gas tube is a filter resistor 7'54. Connected to the other end of resistor 154' is the output terminal 756 and the by-pass or filter condenser 155. An amount of current approximately equal to can be supplied to the negative terminal 156 before the current in the gas tube fails. The circuit of Fig. 6a can thus supply a useful negative voltage output equal to or less in magnitude than EB 2EL at any current drain less than Referring to Fig. 6b, the terminal 1160f winding lid is shown connected to the anode of a diode l6! and to the primary winding 162 of a transformer. The cathode of the diode Hit and the other end of the winding 162 are grounded. Pulses of current drawn by tube llfi from terminal HG pass through the winding I62 and induce voltage pulses across the winding N53. The bottom of winding lit-3 is grounded and the top connects to the anode of diode iii-l. The cathode of diode 'lli l is by-passed to ground by condenser and is also connected to output terminal 7%.. During. the voltage pulses which appear across winding 15-3, the diode 1-64- conducts current and. charges condenser 165., Be-

Accordingly, the, terminal tween these pulses diode 164 is non-conducting. Accordingly, condenser 1 65 becomes charged so that terminal 166 is positive. The, diode 16] serves to damp out any positive voltages which may appear as transients on terminal H6 after each current pulse. The positive voltage developed at terminal 1% can have a wide range of values by choice of the turns ratio of the transformer, and canv also be made negative by reversing the connections of the diode 164 and the sense of winding Hi3. In a typical case, the terminal 166 can be connected to the supply 12! and the condenser I65 can then be omitted. In this case the circuitof Fig. 6b effectively returns current and power to the supply 121, thus further reducing the drain on this supply.

In Fig. 6c, the terminal 116 of winding H4 is shown connectedto a tap III on an inductance 110. The lower end of this inductance is grounded and the upper end connects to the anode of a diode 116 and to a tuning capacity N5, the lower terminal of which is grounded. The cathode of diode H6 connects to an output terminal H8 and to afilter or by-pass condenser 11! the lower terminal of which is grounded. A second tap 1'52 on inductance H0 is connected to the plate of a diode 113, the cathode of which connects through terminal TM to a positive reference voltage source, such as supply l2l. The inductance Till and the capacity 115 are chosen so that together they resonate at the fundamental frequency of saw-tooth waves applied to the output stagev Ill-l. Pulses of current drawn by tube H0 from terminal H6 excite the tuned circuit comprising inductance I10 and capacity I15, causing a substantially sinusoidal voltage to appear across these elements. On the peaks of this sinusoidalvoltage wave, diode H6 conducts and charges condenser I'll: positively. As the oscillation continues to build up; the positive excursion of tap 1-12 soon becomes sufiicient to cause diode T13 to conduct anddeliver current to terminal TM (and thus to source 'IZI). The conduction of diode H3 thus limits the amplitude of the oscillation and a substantially constant positive voltage is developed at terminal 118. By suitable choice of the inductance TH) and the tap positions TH and H2 this output voltage can be made. as high as several kilovolts. The circuit of Fig. 6c is thus a suitable second anode supply for the cathoderay tube. When no current is being drawn from terminal "8, diode 113 conducts a larger current and returns the unused power to the supply 12!. In practice, diode H3 can be one-half of a twin diode'tube, the other half of which is used as diode 121 in Fig. 5.

It should be noted that the power obtained from any of these power utilization devices is free in the sense that this power would otherwise be wasted as plate dissipation in tube H0. The use of any of these-devices imposesno further load on the deflection circuit and requires no increase in plate drain from the supply 121. In fact, the current drain from the supply 1-2! is reduced with certain of the devices. This is in contradistinction to the conventional type of fly-back high voltage supply associated with the horizontal deflection circuit in certain television applications. There, the rectification of the high voltage during fly-back damps the return oscillation-of the deflection circuit, and this in turn requires an increase in the current requirement ofthe driver stage.

If for. anyreason the reactive: voltage from the load is insufficient to provide plate voltage for tube H0, a supplemental source (smaller than the supply 12 I) can be provided in the plate circuit of tube H0.

Various modifications, other than those specifically mentioned above, can be made in the embodiments described above without departing from the spirit of the invention, the scope .of

1. A circuit arrangement comprising a first "and a second control device each having an input and an output circuit, means for applying to each of said input circuits an input wave, a reactive load, a power source in the output circuit of the first only of said devices, means comprising said first device and said power source for supplying energy to said load during one portion of said wave, and means comprising the second of said devices for controlling the removal of energy from said load during another portion of said wave.

2. A circuit arrangement for generating a sweep wave having a forward or sweeping portion and a fly-back portion, comprising a first and a second control device each having an input and an output circuit, means for applying to each of said input circuits an input wave, a reactive load, a power source in the output circuit of the first of said devices, means comprising said first device and said power source for supplying energy to said load during one-half of thesweeping portion of said wave thereby storing energy in said load, and means comprising the second of said devices for controlling the removal of energy from said load during the other half of the sweepin portion of said wave.

3. A circuit arrangement comprising a first and a second control device each having an input and an output circuit, means for applying to each of said input circuits in push-pull manner an input wave, a reactive load, a power source in the output circuit of the first only of said devices, means comprising said first device and said power source for supplying energy to means comprising the second of said devices for,

controlling the removal of energy from said load during another portion of said wave.

4. A circuit arrangementcomprising two control devices each having an input and an output circuit, means for applying to each of said input circuits an input wave, a reactive load, a power source in the output circuit of one of said devices, means comprising said one device and said power source for supplying energy to said load during one portion of said wave, means comprising the second of said devices for controlling the removal of energy from said load during another portion of said wave, and means apart from said load and in the output circuit of said second device for utilizing energy removed from said load.

5. Acircuit arrangement comprising two space current devices each having an input and an output circuit, means for applying to each of said input circuits an input wave, a reactive load, a power source in the output circuit of one only of said devices, means comprising said one device and said power source for supplying energy to said load during one portion of said wave, means comprising the second of said devices for controlling the removal of energy from said load during another portion of said wave, and means apart from said load for utilizing energy removed from said load. 7

6. A circuit arrangement comprising two control devices each having an input and an output circuit, means for applying to each of said input circuits an input wave, a reactive load, a power source in the output circuit of one only of said devices, means comprising said one device and said power source for supplying energy to said load during one portion of said wave, and means comprising the second of said devices ior controlling the removal of energy from said load during another portion of said wave.

'7. An amplifier circuit comprising two electron discharge devices each having an input and an output circuit, means for applying in pushpull manner to the input circuits of said two devices a saw-tooth wave each cycle of which has a sweeping portion and a return portion, a reactive load, means including a source of direct potential connected in the output circuit of the first of said devices for storing energy in said reactive load for a part of the sweeping portion of each cycle of the saw-tooth wave, and means including said reactive load for returning power from said reactive load to the output circuit of the second of said devices during another part of said sweeping portion of each cycle.

8. An amplifier circuit comprising two electron discharge devices each having an input and an output circuit, means for applying in pushpull manner to the input circuits of said two devices a saw-tooth Wave each cycle of which has a sweeping portion and a return portion, a reactive load including a transformer having two primary windings and a secondary winding with an inductive element connected thereto, means including a source of direct potential connected in the output circuit of the first of said devices and one of said primary windings for storing energy in the reactive load for part of the sweeping portion of each cycle of the saw-tooth wave, and means including said second primary winding and said secondary winding for returning power from the reactive load to the output circuit of the second of said devices during another part of the sweeping portion of each cycle.

9. An amplifier circuit comprising two electron discharge devices each having an input and an output circuit, means fOr applying in push-pull manner to the input circuits of said two devices an input voltage wave having a portion during which the potential change in one direction is accomplished within a certain time period and another portion during which the potential change in the opposite direction is accomplished within a shorter time period, a reactive load, means including a source of direct potential connected in the output circuit of the first of said devices for storing energy in said load for a part of the firstmentioned portion of the input wave, and means including said load for returning power from the reactive load to the output circuit of the second of said devices during another part of said firstmentioned portion of said input wave.

10. An amplifier circuit comprising two electron discharge dcvices each having an input and an output circuit, means for applying in pushpull manner to the input circuits of said two devices an input voltage wave having a portion during which the potential change in one direction is accomplished within a certain time period and another portion during which the potential change in the opposite direction is accomplished within a shorter time period, a reactive load, means including a source of direct potential connected in the output circuit of the first of said devices for storing energy in said load for a part of the first-mentioned portion of the input wave, and means for taking a voltage from the output circuit of said second device which is larger than the voltage of said source of direct potential.

11. An amplifier circuit for a non-sinusoidal Wave of the type in which there is a relatively slow variation in one direction followed by a relatively rapid variation in the opposite direction, comprising a first amplifier, an output stage amplifier connected to said first amplifier, said output stage amplifier comprising two tubes each including an anode, a cathode and a control element, a reactive load connected to both anodes, a source of direct potential, means for applying anode voltage from the source of direct potential to one only of said tubes, means for returning power from said reactive load to supply anode voltage for the second of said tubes. and means for feeding back energy from said load to said first amplifier.

12. An amplifier circuit for a voltage variation having a relatively slow change in one direction followed by a relatively rapid change in the opposite direction, comprising'two tubes eachhaving an anode, a cathode and a control element, means for applying said voltage variation in push-pull manner to the control element-cathode circuits of said two tubes, a reactive load, means for connecting said output circuits in push-pull manner to said reactive load, a source of direct potential, means for applying said source to the anodecathode circuit of the first of said tubes only, and means including said reactive load for applying anode voltage to the second of said tubes.

13. An amplifier circuit for an input wave comprising two tubes each having an input and an output circuit, means for applying said input wave in push-pull manner to both input circuits, a common load, means for connecting each of said output circuits to said load, and means for applying direct otential to the output circuit of one only of said two tubes.

14. An amplifier circuit for an input wave having a substantially slow variation in one direction followed by a relatively fast variation in the opposite direction comprising two tubes each havin an anode, a cathode, a control element and a screen grid, a reactive load, means for applying said input wave in push-pull manner between the anode and cathode of each of said tubes, means for connecting both of said anodes to said reactive load, means for applying direct potential to the anode of one only of said tubes, means for maintaining both screen grids at all times positive with respect to their corresponding cathodes, and means for decreasing said screen grid potential during the rapidly varying part of said input wave.

15. An amplifier circuit including an anode, a cathode, a control element and a screen grid, means for applying an input wave between the control element and cathode of said device of such form that it causes said grid to vary both positively and negatively with respect to said cathode, means for applying a potential between the anode and the cathode of said device which causes said anode to at times have a potential which is negative with respect to said cathode, means for applying a potential to said screen grid which is at all times positive with respect to said cathode, and means for decreasing the value of said screen grid potential whenever, at the same time, the control element potential is positive with respect to said cathode and said anode voltage is negative with respect thereto.

16. An amplifier circuit including an anode, a cathode, a control element and a screen grid, means for applying an input wave between the control element and cathode of said device of such form that it causes said grid to vary both positively and negatively with respect to said cathode, means for applying a potential between the anode and the cathode of said device which ,causes said anode to at times have a potential which is at all times positive with respect to said cathode, and means for decreasing the value of said screen grid potential whenever, at the same time, the control element potential is positive with respect to said cathode and said anode voltage is negative with respect thereto, said lastmentioned means including a, diode which is normally conducting but which becomes non-conducting when the screen grid current exceeds a predetermined amount.

17. An amplifier for sweep waves which are adapted to be applied to the deflecting coils of a cathode ray tube, said sweep wave having a forward portion and a return portion, comprising two tubes, means for applying the sweep wave to both of said tubes, a reactive load, circuit means for applying energy from one of said tubes to said load during one part of the forward portion of said sweep wave, and means for returning energy from said reactive load to said other tube during another portion of the forward sweep of said input wave.

BERNARD M. OLIVER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,180,365 Norton Nov. 21, 1939 2,280,733 Tolson Apr. 21, 1942 2,280,990 White Apr. 28, 1942 

